One-phase stepping motors convert electrical impulses of alternating polarity into step-by-step rotating movements. Such motors have a magnetic asymmetry for purposes of determination of the direction of rotation. In the one-phase stepping motor of Swiss Pat. No. 541,893, the magnetic asymmetry is achieved by providing a stator comprising main poles and auxiliary poles. Typically, the main poles are excited by a current resulting from the above-mentioned electrical pulses of alternating polarity. The auxiliary poles are permanently magnetized. The auxiliary poles are displaced vis-a-vis the main poles by an angle of 45.degree. el and are arranged in such a way that no torque is produced by the auxiliary poles as a result of the current used to excite the main poles. The two types of poles are formed inside a two-part housing. In particular, the auxiliary poles are formed integral with and extend inward from the top and bottom surfaces of the housing.
The object of the present invention is to provide a one-phase stepping motor that cannot be influenced by external magnetic fields and which produces a minimal amount of stray magnetic fields.